Shawn MacDonald, foreground, and Tammy Strey-Hirt of Clintonville, listen during a question and answer session regarding the unexplained booming noises being heard as citizens and members of the media gather at Clintonville High School in Clintonville, Wis., to ask questions of officials on Wednesday.

Chicago — Before this week, Clintonville, Wis., a small manufacturing city 40 miles west of Green Bay, would hardly have been mistaken for a boomtown.

That changed with a flurry of mysterious and disconcerting overnight booms and vibrations that kept Clintonville residents nervously awake for three consecutive nights. The sonic interruptions brought national media to Clintonville and prompted city officials to hire an engineering firm Wednesday to figure out what is going on.

The intermittent underground booms began sounding in the wee hours early Monday morning, spurring about 150 calls to the city’s emergency response center and spreading fear among residents that something is happening that may affect not only their sleeping patterns but the structure of their homes.

“The cracks in my floor, the cracks in my wall are getting worse,” Sharon Binger said Wednesday night at a town hall meeting held at a local high school that attracted about 400 residents. The booms are powerful enough to rattle dishes, say some, while others describe the sounds as underground fireworks.

The city announced it is spending $7,000 for an engineering firm based in Waukesha, Wis., to study the sounds by placing four seismometers in the area to determine from how deep into the earth the booms are originating. The city set up its own audio and video surveillance equipment Wednesday night, but nothing was captured except a single boom around 5 a.m.

Lisa Kuss, the city administrator, tried to prepare residents Wednesday for the possibility the mystery will never be solved. “It’s possible [they will] never have a definitive answer” to what is causing the sounds, she said.

The booms were first reported between 1:45 a.m. and 8 a.m. Monday, and continued sporadically later that day. While the volume of reports has subsided since that time, residents continue to report the noise disrupting their sleep and unsettling their nerves.

So far, investigations into possible sources have proved fruitless. Ms. Kuss says there are no military or mining operations in the area, and the city checked a nearby landfill to determine if it was emitting methane gas. The National Weather Service says no earthquakes have been reported earlier this week.

Geologists are equally stumped, though one theory blames the weather.

Steve Dutch, a geologist at the University of Wisconsin at Green Bay, told the Associated Press that low levels in the underground water table may be forcing granite rocks to settle in the gaps, triggering disruptive noises. The falling water levels, Mr. Dutch says, could be caused by “the very dry winter.”

At Wednesday’s public meeting, Chuck Sitzwohl said the underground noise originated long before this week.

“I’ve heard this noise a few week ago and I swear, for a few years now, every so often you’d heard a thump,” Mr. Sitzwohl said. “For a few years, we’d hear it and then a month later, you’d hear it again.”